Which Indian state is not part of the 'Seven Sisters' of North-East India?

The correct answer is Sikkim . Key Points The Seven Sister States is a popular designation for the contiguous states of Northeastern India , comprising Arunachal Pradesh , Assam , Meghalaya , Manipur , Mizoram , Nagaland , and Tripura . Sikkim is not included in the Seven Sisters because it is geographically separated from the other seven states by the Siliguri Corridor , also known as the Chicken's Neck , in West Bengal . The term was first coined in January 1972 by Jyoti Prasad Saikia , a journalist and civil servant from Tripura , during a radio talk show to coincide with the formation of the new states. While Sikkim was formally integrated into the North Eastern Council (NEC) in December 2002 , it is historically and culturally regarded as the Brother to the Seven Sisters rather than a member of the group itself. The Seven Sisters share a unique ecosystem and are bordered by Bhutan , China , Myanmar , and Bangladesh , sharing only a small land connection with the rest of India . Additional Information Assam : The gateway to the Northeast , it is famous for its Tea production, the Brahmaputra River , and the One-horned Rhinoceros found in Kaziranga National Park . Nagaland : Known as the Land of Festivals , its capital is Kohima , and it is widely recognized for the annual Hornbill Festival which showcases the heritage of its 16 major tribes. Mizoram : Located at the southern tip of the North-Eastern region, it shares international borders with Myanmar and Bangladesh and has one of the highest literacy rates in the country. Sikkim : It became the 22nd state of India following the 36th Constitutional Amendment Act in 1975 and is home to Kanchenjunga , the highest mountain peak in India .